Electron discharge device



Nov. 2, 1937.

E. KoBEL.

ELECTRON DISCHARGE DEVICE F`i1ed Dec. 21, 1935 5 sheets-sheet 1 E. KoBl-:L 2,097,490

ELECTRON DISCHARGE DEVICE Nov. 2, 1937.

3 Sheets-Sheet 2 Filed Dec. 2l, 1935 Nov. 2, y1937. E. KoBEL 2,097,490

ELECTRON DI SCHARGE DEV I CE Filed D ec'. 2l, 1933 3 Sheets-Sheet 3 Patented Nov. 2, 1937 ELECTRON DISCHARGE DEVICE Ernst Kobel, Ennetbaden, Switzerland, assigner to Aktiengesellschaft Brown Bovcri 52l Cie., Baden, Switzerland, a joint-stock vcompany of Switzerland Application December 21, 1933, Serin N0. 703,349 In Germany December 24, 1932.

8 Claims.

This invention relates generally to electron' valve in which current is conducted through al gas or a vapor.

A large number of different kinds of electric valves of the vapor type are known in which current is conducted between one or more anodes and one or more cathodes through attenuated gas or vapor or sometimes through air at atmospheric pressure. the iiow of current is effected almost entirely by the flow of electrons between the cathodeand the anode, such electrons Abeing primarily produced at the cathode by the thermalemission of a lament maintained at incandescence or of an incandescent spot of a mercury pool, or by other processes in valves utilizing cold cathodes. The vapor contained within the valve is then :ionized by collision of such electrons to an'eri#YK charge ofthe electrons which tends to hinder I suclr ow is substantially neutralized. y

Such valves are frequently provided with control electrodes, but although the control electrodes known heretofore were operative to preventV andto release the iiow of current through the valve in dependence upon the 'potential ofy such control electrodes; the oW of the current could not be interrupted thereby after being once established. Such result is due to the fact that when a control electrode is negatively energized with respect to the associatedcathode, it becomes Ysurrounded by a sheath of positive ions which completely absorbs the potential'diiference between 'theV control' electrode and the cathode. The grid therefore becomes incapable ofpconvtrolling conditions within the valve outside of the ion sheath.

If, however, means are provided for removing the positive charges of the ions within the dist charge path, over, atleast a portion of the length thereof, by neutralizing such charges at a rate greater than the rate of appearance thereof, it,

It is generally considered thatV means of a control electrode suitably arranged and of suitable dimensions.

The initiation of a discharge or arc from theV anode may then require energization ofthe control electrode` at a positive potential and this potential may advantageously be reducedl if an auxiliaryr or excitation discharge is caused to occur through the space adjacent'the vcontrol electrode. Such excitation vdischarge als'opr'o'- vides ionized vapory in the spacebetween the anode and the control electrode during operation of the anode, thereby neutralizing the electronic space chargey in such space and decreasing the voltage drop olf the discharge. of current through the anode is interrupted by theaction'of the control electrode, the magneticl When the lilow. A

energy stored in the anodev circuit will cause appearance ofa voltage surge at the anode which is preferably dissipated over a suitable discharge path.

It is, therefore, one of the objects of the present invention to provide an electron discharge device of the gas or'vapor type in which current flowing from an anode to cathode can be interruptedas well as released by control means while the anodeV is positive with respect to the cathode. i

Another object of the present invention is to provide an electron discharge device of `the gas or vapor'type in which the current ilowing from an anode to a cathode'can be interrupted by energizing a control electrode at a negative poten-v tial less'than the potential Vwhich would producey backring Aof`such electrode. K

Another object of the present invention Vis to provide an electron discharge device of the gas or vapor type inV which the ow of current throughV an anode is initiated and maintained by the ionizing action of an'excitation'discharge.

Another object of the present invention is toV provide an electron discharge device of the gas or vapor type in which Voltage surges appearing on the anode are diverted over a discharge path.v

Another object of the present invention is to provide an electron discharge device of thegas or vapor type in whichra portion of the discharge path maybe deionized to permit control and interruption of the discharge.

Objects and advantages other than those above described will be apparent from` ther following description when' read in connection with the accompanying drawings, Vin which:

Fig. 1 illustrates, in cross-section,V an. anode A structure forv an electron discharge device havlng a` control electrode and an auxiliaryv elecfcause the discharge to occur only `present invention;

Figs. 8 and 9`illustrate a portion of another embodiment of the present invention utilizing separate deionizing electrode; and

Fig. 10 Vdiagramrnatically illustrates an example of one of the numerous possible'connectionsof an electron discharge device constructed in accordance with the present invention and utilized as an alternating current rectier.

Referring more particularlylto the drawings byV characters of reference, reference numeral IIV designates the casing wall of a discontinuously controllable electron discharge device such as an.

electric valve of the vapor.type and having an aperture therethrough receiving the anode struc-` ture to be hereinafter described. An insulator bushing I2 extends lthrough such aperture and is supported from wall II by suitable means such as a split collar I3 bolted on the wall.V The joint between wall I I and insulator I2 is'sealed by vany means known in the art whereby a gas tight joint wmay be obtained. VInsulator I2 supports an anode I4 having a stem portion extending through the insulator and a head portion receiving the discharge. The head portion of the anode is pressed against the lower part of the insulator by suitable means (not shown) and the anode is sealed against the insulator in any suitable manner. It will be understood that anode I4 maybe constituted of any suitable conductive materials and g may be constructed with a plurality of separate portions of diierent materials. Anode I4 willY 'K generally present a cylindrical surface Iand an end 'surface lI'I although anodesof anyother suitable shape and construction Vmay be used.V

Anode I4 is associated with a control electrode generally designated I8 having dimensions to be more particularly specied hereinafter. In the present embodiment, control electrode" I8 is represented as comprising a perforated plate I9 pro- Videdjwith reinforcing' ribs and supported from insulator I2 by an unperforated 'cylinder 2| and a ring 22 provided with set screws resting corrugations of insulator I2. To force the discharge to pass only throughA thefa'p'ertures of plate I9, ring 22 is sealed against insulator I2 by a sealing ring 24. The discharge alsoV comesinto Contact with an auxiliary electrode 26 herein 'constituted bya plate'having large perforations and reinforced by .a ring 21. VElectrode 26 is supported within a discharge guide 28 by means of suitable insulators 29. Electrodes I9 and 26 are connected with suitable energizing means through insulated leads 3I. Guide 28 is preferably supported from insulator I2 in sealing engagement therewith to through the lower part of the guide. Y

In the modification illustrated inFigrs. 2 and 3, plateV I9'of control electrode i8 `is replaced by a perforated plate 32 provided with a pluralityV of parallel fins 33 constituting collecting surfaces for the charges of positive ions present in theV space between the anode I4 and control electrode I8.

In the embodiment illustrated in Figs. 4 and 5,

plate IS is replaced byY a perforated plate 34 pro- Videdrwith a plurality ofkr pins 36 havingV the same Y purpose as iins 33'in Figs. 2 and 3.

In the embodimentillustrated in`Figs. 6 and '7, the control electrode `I8 consists of finnedplate 32 and of a cylindrical portion 3l'made in two .parts attached to plate 32 by means of ja ring 39,

Y corrugation of insulator I2.

Vand 7 but not provided with'interior ns.

and provided with'a flange portion resting in a Cylinder 3'I is provided with a plurality of annular iins 38 having the same purpose as ns 33 of plate 32 and is preferably perforated in the same manner as the plate. Anode I4 may be provided with parallel fins 42 occupying the spaces between ns 33 and with annular ns 4I occupying the spaces between ns 38.-

; 1: Inthe embodiment illustrated in Figs. Sand 9 control electrode I8 comprises a cylindrical portion 43 and a'plate 4'I similar to cylinder 3'I and `plate'32 of the embodiment illustrated in Figs. 6 In the present embodiment such fins are replaced by a separate ion collectingV electrode structure 44 comprising a plurality of annular members supported on cylinder 43 by means of insulators 43 and a plurality of rectilinear'members supported in plate 4'I by insulators 49. The electrode structure 441s connected Withra suitable energizing means to be described hereinafter by source. To obtainsuch interruption the positive charges of the ions present overa portion of the length oi the discharge path, such as for instance V in the space betweenuthre anode and the control electrode, must be largely eliminated. In other words, the ionic charges within such space must v be removed at a rate greater than the rate of appearance of such chargesas the result either Vof collisions of the electrons with vapor atoms therein or of wandering of ions from the space outside the control electrode through the openings thereof. Upon substantially complete removal of such charges the control electrode becomes operative toV control or to completely interrupt the flow of electrons therethrough, the complete interruption being obtained by impressing a suitable negative potential on the control electrode to prevent any further transport of charges at the anode'. To obtain such result without re- Y sorting to the use 'of a source of such high voltage as tointroduce disturbances in the operation of vthe device,`it'is necessary toY employ control electrodes having dimensions maintained within presible to de ne thepermissible rangeffor all dimensions of the control `electrode because the dimensions of each portionjthereof limitfthe determined limitations. It is,`however, vnot pospermissible range of dimensions of all the other portions and all' `such dimensions are dependent upon the nature of the yvapor carrying the discharge, the temperature, the pressure and the" degree of ionization thereof, as well as upon the potentials'impressed between the control electrode and the cathode and between the anode and the cathode, and on the amount of current flowing therebetween. lIt has been found that the desiredresultis accomplished, in particular,

control` electrode is unenergized or is energized at negative potentials of any magnitude with'respect to the associated cathode. lIrrespective of such condition, the openings of the control electrode should preferably be of dimensions less than twice the mean free path of the electrons in the device to substantially prevent ionization by collision within such openings and thus facilitate the deionizing action of the electrode. total area of such openings must also be limited and should preferably not exceed 40% of the areak of the anode carrying the discharge. The distance between the control electrode and the anode should be comparable with the mean free path of the electrons, butV should not exceed fifty times the greatest dimension of such openings. The area of the control electrode in Contact with the space contained between such electrode and the associated anode, plus the total area of the surfaces of such control electrode forming the openings thereof, which surfaces jointly operate to collect the charges of positive ions present in the space between the control electrode and the anode, should be greater to a variable extent than the total cross-section area of such openings. The lower limit of the ratio of such areas varies with the distance between the control electrode and the anode and should exceed the value 2.5 in a device utilizing mercury vapor when such distance is equal to the mean free path of the electrons. It will be understood that such dimensions are given only as an example of constructions which have been found successful by experiment but that vsuchdimensions Vand the Y arrangement of the control electrode may be departed from to a considerable extent. Withthe above dimensions, it is possible to interrupt current through an anode by impressing on the control electrode a negative potential less than the amplitude of the positive potential of the anode immediately after interruption of the current therethrough.

The effectiveness of control electrode I8 may be impaired if the space adjacent such control electrode contains appreciable amounts of gases or vapors other than the operating vapor. It is, therefore, advantageous to make the control electrode of materials which do not easily adsorb gases or vapors and from which, therefore, gases orV vapors are released in only inappreciable amounts at operating temperatures. materials particularly suitable for the construction of the control electrode are metals or alloys such as nickel, nickel steel, chrome nickel steel,

molybdenum, tungsten and tantalum. The control electrode is preferably made by casting or sintering such metals in vacuumV and may be subsequently heat treated in vacuum to further decrease the foreign gas content of the material.

The method of operation and the scope of the present invention will be more clearly understood from a consideration of the application thereof in the system illustrated in Fig. 10,'which corresponds to the embodiment of the invention as illustrated in Fig. l of the drawings of the Ernst Kobel copending application Serial No. 677,069, filed June 22, 1933, enitled Electron discharge control device; and which is per se claimed therein. In such gure a discharge device 50 is diagrammatically represented as being of the type having a mercury pool cathode 58 and as being provided with a plurality of anode structures similar to anode I4 with the associated control electrode I8, and also provided with' electrodes The.:

, nous motor 58 energized from line 52.

Among the mandes/'ice sans utilized for rectifyingl current transmitteddrorn an' alternating currentzline 52V through a transformer 53 andan 'interphase' transformer 54 to a direct current. line 56 con-Y nected with cathode 50 and the'interphase transformer 54. Each anode I4 is connected with the associated electrode 26 through'a resistor 55, and is connected with the associated control-electrode Iii-through one of the segments cfa distributo-r`5l having a brush driven by'a synchro- Each con-l trol electrode I8 is further connected with a`- source of negative potential with respect to cathode 6E such as battery 63 through onev of the contacts of a distributor 59 driven by a synchronous motor 5I' energized from line` 52. When electrodes such as 44 are utilized, each such electrode is connectedv with a'suitable point of battery 63 either'directly or through a distributor 62 operating in conjunction with distributor 59. Synchronous motors 58 and 6I are each provided with a plurality Aof eld windings receiving exciting current from line 52 through rectifying devices 66 and a regulating device 54 to adjust the moments of energization of the several electrodes of device iI during the voltage cycle of line 52.

In operation, assuming that line 52 is energized and that motors 58 and 6I have been brought to synchronous speed, anode I4 receives, from transformer 53, an alternating voltage recurringly bringing such anode to a positive potential with respect to cathode 5i).` Electrode 26 is then likewise brought to a positive potential and carriesr lot:

a Vcurrent limited by resistor 55, which ionizes and of control electrode I8 with battery 6`3 is eifected through distributors 52 and 59.Y Upon such connection and as a result of the construction and arrangement of control electrode I8 in the manner above specified, the charges of the ions present between control electrode I8 and anode I4 are removed at a rate greater than the rateof appearance of such ions within such space f by collision or by Wandering through the control electrode apertures. As a result of such removal, the space charge ofthe electrons between anode I4 and control electrode I8 is no longer entirely neutralized and the uncompensated fraction of j such space charge causes the electrons originating at cathode @il o'r in the adjacent space to reach anode I4 with greater difculty and, therefore, in' smaller number. The ions produced by collisions of such electrons with vapor atoms, therefore, also appear at a lesser rate whereas the capacity of the electrodes I 8 and 44 to remove such ions remains undiminished, with the result that such ions are removed with increasing ease, and the resulting increasing impedance of the space confined between anode I4 and control electrode I8 causes the flow of electrons Within such space to decrease'to a' value comparable with Vthe flo-w of electrons in avalve ofthe Vacuum type; Such flow of electrons may then be controlled by the action of control electrode I 8 which repels such electrons as'. a result of the negative utilized'at present. Although in the embodiments' illustrated a portion of the space withinVV the device is deionized by either the control electrode alone or the control electrode in'conjunction with an auxiliary electrode, such deionization may be elected by the auxiliary electrode alonefor by any other suitable means. When such space has been deionized, the control of the electronic discharge may'also be eiected by any suitable means other f than the control electrode illustrated in the above described embodiments. If the control electrode is used, it has been found sucient to deionize the space on one side only of such control electrode, but if so desired, the space on both sides of the control electrode may likewise be deionized by the provision of charge collecting surfaces or of equivalent means. It is, of course, necessary that the dischargepath be deionized over the entire cross-sectional area thereof. In the embodiments illustrated, the control ,electrode completely encloses the anode head, but where a discharge guide suchas guide 28 illustrated in Fig. l yis provided, such discharge guidemay cooperate with the control electrode in separating the space surrounding the anodeV head from the space between the control electrode and the cathode. e

Although but afew embodiments of the presentV invention have been illustrated and described, it will be apparent to persons lskilled in theV art that various changes and modifications may be made therein without departing from the spirit of the invention. or from the'scope of the appended claims. i

-said cathode spaced electrodes vfor the flow of cur- .rent by way of arcs through said vapor, and

means for controlling said flow of'current by interruption of said arcs while the said anode is subjected to potential oi sign and magnitude sufficientpto maintain said arcs comprising a control electrode spaced from said Yanode by approximately the mean free path of said electrons and having apertures therethrough' of a' total crosssection area of approximatelyl Yforty-percent ofthe arcing surface of said anode, V,and having a total area in Contact with the space contained between the control electrode and said anode, plus the said cathode spaced electrodes'for thev flow of Ycurrent by Way'of arcs through said vapor, Yand means for controllingV said ow of current by interruption of said arcs while the'saidfanode is subjected topotential of sign and magnitude cease.-v Suchsequenceof Voperation is 'repeated sufficient to maintainsaid arcs comprising aconhaving apertures therethrough of a total crosssection area of approximately lforty percent of the arcing surface of said anodeand having a trol electrode spaced from said anode by approximately the mean free path of said electrons and total area in contact with the space contained between the'control electrode and said anode, plus the total area ofthe rsurfaces forming said.' apertures, of not less than two and a half times the total Ycross-section areaof said apertures, and another 'electrode 'arranged in the path of said arcs between said control electrode and said cathode and connected with said anode.V

3. In an electron discharge device of the vapor arcing type, the combination of a cathode, an anode constituting with said' cathode spaced electrodes forthe ilow of current by way of arcs than the length of the mean free path of electrons involved insustaining said arcs and having apertures defined by opposite surfaces distant not more than twice the thickness of ionsheaths produced within said apertures when subjected to potential more negative than the potential of said cathode.

4. In an electron discharge device of the vapor arcing type, the combination of a cathode, an anode constituting with said cathode spaced electrodes for the flow of current by way of arcs therebetween, and means for controlling said flow of` current by interruption of said arcs during Vperiods when said anode and cathode are subjected torpotential differences of sign and magnitude suflicient to maintain said arcs comprising a control electrode having a surface thereof positioned from the arcing surface of said anode a distance not greater than the length of the mean free path of the electrons involved in sustaining said arcs, and having a plurality of apertures constituting paths for the ow of said current cfa total cross section area of approximately forty percent of the arcing surface'of said anode.

5, In an electron discharge device of the vapor arcing type, the combination of a' cathode, an anode constituting with said cathode spaced electrodes'rfor the ow ofcurrent by way of arcs therebetween, and means for controlling said vflow of current by interruption of said' arcs during periods when said anode and cathode are subjected to potential dilerences sucient to maintainsaid arcs comprising a' control electrode positioned across the path of said arcs and having a plurality of vapertures of a total cross section area of approximately forty percent of the arcing sur-Y face of said anode, and having a total area in concontrol electrode and anode, .plus the total area Yof the surfaces formingi said apertures, of'not Vtact vwitlrthe v,space contained between the said lessthan two' and one-half times the total v'cross Y charge device of thevapr arcing type and constituting spaced electrodes for the-flow of current by way of arcs therebetween, of means'for controlling 4said iiow of current byinterruption of Vsaid arcs during periods whenthe said Vanode and cathode are subjected to potential of sign III! and magnitude sufficient to maintain said arcs comprising a control electrode having a surface thereof positioned at a distance from the arcing surface of said anode not greater than the length of the mean free path of the electrons involved in sustaining said arcs and having a plurality of apertures forming paths for the flow of said current and of such cross section area that the distance between opposite surfaces defining the same is not greater than twice the thickness of ion sheaths produced therein when subjected to a potential more negative than the potential of said cathode, and means comprising an auxiliary electrode having connection with said anode and so positioned relative to said cathode as to constitute therewith spaced electrodes for the discharge of voltage surges occurring upon the said interruption of said arcs.

'7. In an electron discharge device of thevapor arcing type, the combination with an electron emitting cathode supported in contact with a body of ionizable vapor, and an anode positioned to receive electrons from said cathode ionizing said vapor and constituting with said cathode spaced electrodes for the flow of current by way of arcs through said Vapor, of means for controlling said flow of current by interruption of said arcs during periods when said anode is subjected to potential of sign and magnitude sufficient to maintain said arcs comprising a, control electrode having ,a surface thereof positioned at such a distance from the arcing surface of said anode as to deionize the space therebetween when subjected to a potential more negative than the potential of said cathode, and having a plurality of apertures forming paths for the ow of said current of such cross section area that the distance between opposite Surfaces defining the same is not greater than twice the thickness of 40 ion sheaths produced therein when subjected to said potential, and means comprising an auxiliary electrode having apertures forming paths for said arcs positioned in the space between said control electrode and said cathode for deionizing the same upon being subjected to a potential of suitable sign and magnitudeto thereby facilitate the said arc interruption action of said control electrode.

8. The combination in an electron discharge device comprising an evacuated chamber having a cathode of vaporizable material and an anode supported thereon and constituting with said cathode spaced electrodes for the flow of current by way of arcs therebetween, anda shield supported within said chamber about said anode and forming a guide for said arcs, of means forV controlling said flow of current by controlling the initiation and interruption of said arcs during periods when said anode and cathode are subjected to potential differences of sign and magnitude sufficient to maintain said arcs comprising a control electrode supported within said shield with a surface thereof positioned from* f the arcing surface of said anode at a distance not greater than the. length of themeancfree path of electrons involved in sustaining said arcs and having apertures' defined by opposite sur- 

